2 files changed, 52 insertions, 0 deletions

diff --git a/crates/ra_db/src/lib.rs b/crates/ra_db/src/lib.rs
index 33cb0e2ec..6a996c7f4 100644
--- a/crates/ra_db/src/lib.rs
+++ b/crates/ra_db/src/lib.rs
@@ -10,6 +10,7 @@ mod syntax_ptr;
 mod file_resolver;
 mod input;
 mod loc2id;
+pub mod mock;
 
 use std::sync::Arc;
 use ra_editor::LineIndex;
diff --git a/crates/ra_db/src/mock.rs b/crates/ra_db/src/mock.rs
new file mode 100644
index 000000000..2840f9655
--- /dev/null
+++ b/crates/ra_db/src/mock.rs
@@ -0,0 +1,51 @@
+use std::sync::Arc;
+
+use rustc_hash::FxHashSet;
+use relative_path::{RelativePath, RelativePathBuf};
+
+use crate::{FileId, FileResolver, SourceRoot, FileResolverImp};
+
+#[derive(Default, Debug)]
+pub struct FileMap(Vec<(FileId, RelativePathBuf)>);
+
+impl FileMap {
+    pub fn add(&mut self, path: RelativePathBuf) -> FileId {
+        let file_id = FileId((self.0.len() + 1) as u32);
+        self.0.push((file_id, path));
+        file_id
+    }
+
+    pub fn into_source_root(self) -> SourceRoot {
+        let files = self.files();
+        let file_resolver = FileResolverImp::new(Arc::new(self));
+        SourceRoot {
+            file_resolver,
+            files,
+        }
+    }
+
+    pub fn files(&self) -> FxHashSet<FileId> {
+        self.iter().map(|(id, _)| id).collect()
+    }
+
+    fn iter<'a>(&'a self) -> impl Iterator<Item = (FileId, &'a RelativePath)> + 'a {
+        self.0
+            .iter()
+            .map(|(id, path)| (*id, path.as_relative_path()))
+    }
+
+    fn path(&self, id: FileId) -> &RelativePath {
+        self.iter().find(|&(it, _)| it == id).unwrap().1
+    }
+}
+
+impl FileResolver for FileMap {
+    fn file_stem(&self, id: FileId) -> String {
+        self.path(id).file_stem().unwrap().to_string()
+    }
+    fn resolve(&self, id: FileId, rel: &RelativePath) -> Option<FileId> {
+        let path = self.path(id).join(rel).normalize();
+        let id = self.iter().find(|&(_, p)| path == p)?.0;
+        Some(id)
+    }
+}